This invention is generally directed to toner and developer compositions, and more specifically, the present invention relates to negatively charged toners containing composite metal oxides. In process embodiments, the composite metal oxides selected are prepared by treating submicron metal oxide powders, like tin oxide, with a metal halide or a reactive main group element containing reagent, with water vapor, and then optionally with a coupling component, like a fluorinated silane. More specifically composite metal oxides that assist in enabling a negatively charged toner can be prepared by treating, for example, tin oxide particles with silicon tetrachloride, followed by contacting the resulting product with water vapor, and thereafter reacting the product obtained with a fluorinated silane coupling agent. Normally, metal oxides, such as many of the prior art tin oxides when incorporated into toners, provide or assist in providing a positive or weakly negative charge to the toner. In contrast, the composite metal oxides prepared by processes of the present invention when selected for toners provide or assist in providing a pronounced negative charge to the toner of, for example, -10 microcoloumbs per gram to -40 microcoloumbs per gram. Also, toners with the composite metal oxides prepared in accordance with the processes of the present invention possess rapid admix characteristics, such as from between about 15 seconds to about 3 minutes.
The composite metal oxide particles and toner compositions in embodiments of this invention may generally be prepared as described herein, and such processes comprise further aspects of the present invention. In an embodiment of the present invention, the toner compositions are comprised of resin particles, pigment particles, and as a charge and performance enhancing additive composite metal oxide or oxides obtained with the processes of the present invention. One embodiment of the present invention relates to toner compositions comprised of a polymer resin or polyblend mixture, reference U.S. Pat. No. 4,556,624, the disclosure of which is totally incorporated herein by reference, of a first crosslinked polymer, a second polymer, pigment such as carbon black, a wax component, and a metal oxide, such as tin oxide charge enhancing additive obtained with the processes of the present invention, and optional surface additives such as silicas, metal salts, metal salts of fatty acids, or mixtures thereof. The developer compositions of the present invention are comprised of the toners illustrated herein and carrier particles. The carrier particles in embodiments of the present invention are comprised of a core free of a coating or with a polymeric coating, including, for example, a coating thereover generated from a mixture of polymers that are not in close proximity thereto in the triboelectric series, reference U.S. Pat. Nos. 4,935,326 and 4,937,166, the disclosures of which are totally incorporated herein by reference. Developer compositions comprised of the aforementioned toner and carrier particles are useful in electrostatographic or electrophotographic imaging and printing systems, especially xerographic imaging processes, including high speed processes, that is those generating from about 75 to about 125 copies per minute. Additionally, in embodiments, developer compositions comprised of the toners of the present invention and carrier particles of the aforementioned issued U.S. Patent are useful in imaging methods wherein relatively constant conductivity parameters are desired. Furthermore, in the aforementioned imaging processes the triboelectric charge on the carrier particles can be preselected depending, for example, on the polymer composition applied to the carrier core.
Advantages associated with the toners and developers of the present invention in embodiments thereof include desirable toner triboelectric charging characteristics, excellent toner flow properties, excellent toner admix characteristics, excellent color developer formulations for process color and transparency applications, stable performance for extended time periods exceeding, for example, 500,000 imaging test cycles in a xerographic imaging test fixture including those as illustrated in U.S. Pat. Nos. 4,394,429 and 4,368,970, the disclosures of which are totally incorporated herein by reference, the capability to vary the triboelectric charge on the carrier independent of the conductivity thereof; varying the conductivity on the carrier independent of the triboelectric charge thereof; use of the developer in imaging processes wherein a release fluid such as silicone oil is present; use of the developer in imaging processes wherein a minimum amount, or no release fluid, such as silicone oil is present; selection of the developer for electrophotographic, especially xerographic, heated fuser and pressure systems wherein the fuser roll coating is a silicone, reference for example the commercially available Xerox Corporation 1075.RTM. and 1090.RTM. imaging apparatuses; and the like.
Other advantages include providing a convenient and economic process for making composite metal oxide particles; toners and developers thereof; enhanced toner flow; enhanced toner transfer efficiency; and colorless particles for use in multicolor xerography.
Toners with charge additives, including those that impart a positive charge, or negative charge to the toner are known generally. Toner compositions with crosslinked resins and second resins, together with waxes and charge enhancing additives are disclosed, for example, in U.S. Pat. No. 4,556,624, the disclosure of which is totally incorporated herein by reference, and some of the prior art references mentioned thereon, and cited against this patent. More specifically for enhancing the positive charging characteristics of toner compositions there can be incorporated in the toner charge enhancing additives, inclusive of alkyl pyridinium halides, reference U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, organic sulfate or sulfonate compositions, reference U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference; distearyl dimethyl ammonium sulfate, reference U.S. Pat. Nos. 4,560,635 and 4,937,157, the disclosures of which are totally incorporated herein by reference; and other similar known charge enhancing additives including other quaternary ammonium salts. These additives are usually incorporated into the toner in an amount of from about 0.1 percent by weight to about 10, and preferably in an amount of from about 0.1 to about 5, and more preferably from about 0.3 to about 1.0 percent by weight. The triboelectric charge of the toner as determined, for example, by the known Faraday Cage process, or a charge spectrograph is from about 10 to about 40, and preferably from about 15 to about 25 microcoulombs per gram. Toners with negative charge additives, such as aluminum complexes, reference U.S. Pat. No. 4,845,003 are also known. Moreover, other toner formulations containing metal oxides, such as tin oxides generally function as a positive charge additive as is demonstrated in a comparative example.
In a patentability search there were noted the following patents, the disclosures of which are incorporated by reference in their entirety:
Mikami, in U.S. Pat. No. 4,824,754 issued Apr. 25, 1989, discloses a toner particle composition having an inorganic material in or on the toner particle surface. The inorganic material is in the form of particles that have been treated with a titanate coupling agent on the inorganic material surface. The inorganic material is for example a metallic oxide, a carbonate or a silicate.
Kubo et al., in Japanese publication Kokai No.:60[1985]-93,455, published May 25, 1985, disclose developers for electrophotography containing minute particles, for example, colloidal silicon dioxide, treated with a fluorine-substituted silane coupling agent. The toner compositions containing the treated particles afford the following advantages: no fogging of images, extended service life, less dependence on environmental conditions, and excellent fluidity. The treated particles are obtained by spray drying a solution of a silane coupling onto the surface of the metal oxide particles and thereafter the treated particles are admixed with a toner particle composition.
Chatterji et al., in U.S. Pat. No. 3,720,617, issued Mar. 13, 1973, disclose a developer material comprised of colored toner particles having a minor portion of submicroscopic silicon dioxide surface additive particles wherein at least a portion of the silicon atoms on the outside surface of the silicon dioxide particles are attached through an oxygen atom to another silicon atom bearing between one to three carbon atoms.
Geus in U.S. Pat. No. 4,113,658 issued Sep. 12, 1978, discloses a process for depositing by precipitation from aqueous solution a metal or metal compound on the surfaces of support particles resulting in catalytic and magnetic materials, for example, iron oxide dispersed on silica or a mixed cobalt-nickel alloy on silica. The deposited metal or metal compound is obtained in the form of a thin layer or in the form of discrete particles, and, in either form is substantially homogenously distributed over the surface, and is further either crystallographically or electrostatically adhered to the support.
A disadvantage in many prior art methods for preparing metal oxide particulate charge and flow additives is that they do not permit separate adjustment of particle bulk conductivity and particle surface composition. For example, for rapid admix properties high bulk conductivity is preferred, as, for example, as disclosed in U.S. Pat. No. 4,426,436 and for adjusting triboelectric properties, surface modification is usual. Further, prior art methods using solution coating methods using solvents often cause irreversible agglomeration of submicron oxide particles thereby destroying the submicron particle dispersibility and flow-improving capacity on toner surfaces. For example, water slurrys of tin oxide powders dry to permanently or non-friable caked solids.
Thus, there remains a need for black or colored toners wherein toner flow and negative charging properties may be readily attained by the addition of metal oxide composite particles and surface treated metal oxide particles of the insetant invention. Furthermore, there is a need for a composite particle formation process wherein the synthetic yields are high, such as from about 70 percent to nearly quantitative and without resorting to excessive isolation and purification procedures. In addition to the above, there is also a need for black and colored toners that are of excellent image resolution, non-smearing and of excellent triboelectric charging characteristics. In addition, there is a need for black or colored toners with low fusing temperatures, of from about 110 degrees centigrade to about 150 degrees centigrade as determined by known minimum fix temperature techniques and glass transition temperature measurements, of high gloss properties such as from about 50 gloss units to about 85 gloss units as measured by a VWR 75.degree. gloss meter, of high projection efficiency, such as from about 75 percent efficiency to about 95 percent efficiency or more, and, in addition, result in minimal or no paper curl.